Discharge printing of textiles



\ Patented. June 22, 1943 Cumberland, MIL, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application April 16, 1941, I

Serial No. 388,796 i 7 Claims. (01. 8-64) Thisinvention relates to an improvement in the discharge printing of textile materials and relates more particularly to the formulation of printing pastes used in'the discharge printing of fabrics dyed in dark shades with azo dyes so that more desirable illuminated discharge patterns may be obtained.

An object of our invention is the preparation of discharge" printing pastes and the discharge printing, with said pastes, of fabrics dyed in dark shades with azo dyes to obtain clear, bright and.

Y widely used in the dyeing art for obtaining pattern'eilects on fabrics in a simple and economic manner. Generally, the fabric which is to be printed is dyed in the piece in a solid color by means of a suitabledyestufl to provide the color desired as the background. When the fabric is dyed with an azo dyestufl, a chemically active discharge-paste, having a reducing action on mit it to penetrate the fabric, a reducing agent for the dyes used both for the ground color and as the illuminant, generally a sulfoxylate formaldehyde such as sodium or potassium sulfoxylate formaldehyde, and when organic derivative of cellulose fabrics are treated, also preierably'contains a swelling agent to permit better penetra tion of the fabric by the reducing agent, a thickener to keep the'paste from spreading or creeping and enough water to make a thick paste. Illuminated discharge prints obtained on. dark. azo-dyed backgrounds by using discharge pastes containing the above-mentioned alkalies for solubilizin'g the vat dyestuffs were frequently unsatisfactory, however, since the color value of the discharge pattern obtained was poor, due to uneven penetration. This resulted in the presence of a halo ofpartially undischarged backthe azo dye forming the background color, is applied to the fabric in a predetermined pattern and the fabric then treated so that the azo dye is reduced and split at the diazo group and the'background color is removed at the points where the paste has been applied, yielding a.

white pattern or design upon a colored background. When it is desired to obtain a pattern or design in color instead of white, that/is, an illuminated discharge print, it, is preferable to apply, simultaneously with thedestruction of the ground color, a dyestuil" which is either resistant to reduction and is itself a dye for the fabric or one which can be reversibly oxidized after being vatted to the leuco form. In general, it is the vat dyestufis which may be used for illumination since these dyestuffs are capable of being ground colorv about the edges 'of the illuminated discharge pattern, and a mottled appearance in the print. I

We have now discovered that when certain salts of weak acids of boron, silicon and sulfur which have a basic reaction in aqueous solution are incorporated in' discharge printing pastes containing vat dyes to solubilize said dyes, instead ofthe .alkaline compounds heretofore incorporated therein, improved results are secured.

, The illuminated discharge patterns obtained by using pastes-containing these solubilizing salts are clean, sharp, bright and unmottled. In, addition these printing pastes have excellent color value and the objectionable halo about the edges of the discharge pattern is no longer obtained.

.' and sulfur which may beadded to the discharge The salts of the weak acids of boron, silicon printing pastes to solubilize the vat dyes are, as stated, those'salts which have a basic reaction in aqueous solution, Examples of the salts which may be employed in accordance with our invention are the alkali metal salts of sulfurous acid,

tetraboric acld,-hydrogen sulfide, andorthosllicic acid such as sodium silicate, sodium sulfide, sodium borate and sodium sulflte.

As a ground color, any suitable azo dyestuii maybe used. Our invention is particularly of importancein connection with the illuminated discharge printing of fabrics which have been dyed with azo dyes which upon reduction by the discharge agent form products which are reasonably soluble in water.

The discharge paste may be locally applied to the fabric by any suitable means such as printing with embossed or engraved rollers, by stencilling or with blocks.

and the color destroyed. The continuous ager or cottage ager may be used and the ageing.

is generally carried out at about 98 C. to 101 C. for a period of time sufficient to discharge the azo dye. This period may be from about 10 to 20 minutes depending on the type of fabric and the particular dyestuffs used. The fabric is then washed to remove the decomposition products as completely as possible and to wash out the alkaline solubilizing agent so that the insoluble leuco vat is precipitated. The dye may then be oxidized from the leuco form by exposure to air or by an oxidizing bath. After a final wash with water the fabric is dried.

While our invention is applicable to the treatment of azo dyed textile materials generally, it is of particular importance with respect to fabrics or other textile material made of or containing yarns or filaments of an organic derivative of cellulose. As examples of such derivatives there may be mentioned cellulose esters, for example, cellulose acetate, cellulose propionate, cellulose butyrate, mixed esters such as cellulose acetatepropionate and cellulose acetate-butyrate, and cellulose ethers, for example, ethyl cellulose and benzyl cellulose. Mixed materials containing one or more of the aforementioned cellulose derivatives together with other textile fibers may likewise be treated in accordance with our invention. Such materials may contain, for instance, in addition to a cellulose ester or ether, cotton, wool, silk or a regenerated cellulose type of artificial silk.

In order to illustrate our invention but without being limited thereto the following examples are given:

Example I Parts by weight Indanthrene Golden Yellow GK (Schultz Farbstofitabellen 7th edition volume 2,

page 130) l1 Indanthrene Flavone G (a vat dye) 11 Ponsol Jade Green (Color Index No. 1101)-- 2 Sodium sulfox-ylate formaldehyde"; 20 Sodium thiocyanate 45 Supertex gum 96 Sodium benzyl sulphanilate Water 64 Sodium silicate The printed fabric is then dried and aged in the rapid ager for 12 minutes at 100 C. to reduce the azo ground color. The reduction products are removed and the leuco vat dye precipitated by washing the fabric in an aqueous solution containing 2 grams per liter of sodium hydroxide. The fabric is then worked for 2 minutes in a bath containing 5 grams per liter soap maintained at 50 C., thereby oxidizing the leuco vat dye in the discharge pattern. After a thorough rinsing in clear, cold water the fabric is dried and the resulting fabric has a bright greenish figure on a sepia brown background. The printed pattern is distinguished for its sharpness, clearness and excellent. color value, and for its freedom from any halo about the edges of the printed figure.

Example II A cellulose acetic fabric is dyed with 1.25% of Celliton Discharge Blue 5G and 1% of Celliton Discharge Yellow 3GN (an azo dye). This yields a fabric dyed a bright. green shade. The dyed fabric is then printed with a discharge paste made up as follows:

' Parts by weight Indanthrene Scarlet B (a vat dye) Sodium sulfoxylate formaldehyde Sodium thiocyanate Supertex gum Sodium benzyl sulfanilate 5 Water 60 Sodium sulfite 10 After drying in the usual manner, the fabric is aged for 12 minutes at C. in order to reduce the vat to the leuco form and discharge 1 a thorough rinse in clear, cold water, the fabric is dried, finished, and tentered in the usual manner. The resulting fabric has a bright scarlet figure on a bright green ground. The printed. pattern is unique for its sharpness, clearness, and freedom from haloing.

It is to be understood that the foregoing detailed description is given mer'ely by way of iilustration and that many. variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the production of illuminated discharge effects on an azo-dyed textile material, which comprises locally applying to said dyed material a reducing discharge Paste comprising a vat dyestuii" and, as the sole alkaline reacting substance, a salt of a weak acid of a member of the group consisting of boron, silicon and sulfur which has a basic reaction in aqueous solution, subjecting the treated material to ageing, whereby said azo dye is decomposed by 'means of said paste, removing the decomposition comprising a vat dyestuf! and, as the sole alkaline reacting substance, a salt of a weak acid of a member of "the group consisting of boron, silicon. and sulfur which has a basic reaction in aqueous solution, subjecting'the treated material to ageing, whereby said azo dye is decomcomprises printing said dyed material in a pre posed by means of said paste, removing the decomposition products of said discharged azo dyestuff and subjecting saidmaterial to oxidation to illuminate the portions of the material printed with the vat dye.

3. Process for the production of illuminated discharge eifects on an azo-dyed textile'material containing yarns of cellulose acetate, which comprises locally applying to said dyed material a reducing discharge paste comprising a vat dyedetermined pattern with a reducing discharge paste containing a vat dyestufl and, as sole alstud and, as the sole alkaline reacting substance, a salt of a weak'acid of a member of the jecting said material to oxidation to illuminatethe p rtions of the material printed with the vat dye. v

4, Process for the production of illuminated discharge effects on an azo-dyed textile material containing yarns of cellulose acetate, which comprises printing said dyed material in a predetermined pattern with a reducing discharge to remove decomposition products of said discharged azo dyestuif and subjecting said material to oxidation to illuminate the portions printed with the vat dyestufl.

5. Process for the production of illuminated discharge effects on an azo-dyed textile material containing yarns of cellulose acetate, which kaline reacting substance, sodium silicate, subjecting the printed material to ageing so as to decompose said azo dyestufl by means of said discharge paste, washing said textile material to remove decomposition products of said discharged azo dyestufi and subjecting said material to oxidation to illuminate the portions printed with the vat dyestufl.

6. Process for the production of illuminated discharge efiects on an azo-dyed textile material containing yarns'ot cellulose acetate, which comprises printing said dyed'material in a predetermined pattern with a reducing discharge paste containing a vat dystufi and, as sole alkaline reacting substance, sodium sulfite, subjecting the printed material to ageing so as to decompose said azo dyestufi by means of said discharge paste, washing said textile material to remove decomposition products of said discharged azo dyestufi and subjecting said material to oxidation to illuminate the portions printed with the vat dyestuif.

'7. Process for the production of illuminated discharge effects on an azo-dyed textile material containing yarns of cellulose acetata'which comprises printing said dyed material 'in a predetermined pattern with a reducing discharge paste containing a vat dyestufi' and, as sole alkaline reacting substance, sodium sulfide, subjecting the printed material to ageing-so as to decompose .said azo dyest-uif by means of said discharge paste, washing said textile material to remove decompositon products 01 said discharged azo dyestufl. and subjecting said material to oxidation to illuminate the portions printed with the vat .dyestufl'. l v

GEORGE W. SEYMOUR. GEORGE C. WARD. 

